1. Field of the Invention
The invention relates to a system for displaying images including a display panel, and more particularly to a capacitor layout design for an organic light emitting diode display panel and a fabrication method thereof.
2. Description of the Related Art
Recently, organic light emitting diode (OLED) displays have been applied widely to display elements of various products. Of OLED displays, an active matrix organic light emitting diode (AMOLED) display usually utilizes thin film transistors (TFTs) for a switching element of a pixel area and for a driving element of a light emitting element.
Referring to FIG. 1, a schematic circuit of a pixel unit 100 of a conventional active matrix organic light emitting diode (AMOLED) display is shown. The pixel unit 100 has a driving TFT 112 for driving a light emitting element 116 such as an organic light emitting diode (OLED). In addition, a switching TFT 106 is applied to switch the states of the pixel unit 100 and a storage capacitor 108 is to store image data. A gate of the switching TFT 106 is coupled to a scanning line 102, a drain of the switching TFT 106 is coupled to a data line 104 and a source of the switching TFT 106 is coupled to one terminal of the storage capacitor 108 and a gate of the driving TFT 112. In addition, another terminal of the storage capacitor 108 is coupled to a power line 114 through a capacitor line 110 and coupled to a source of the driving TFT 112. Two terminals of the light emitting element 116 are coupled to an anode 118 and a cathode 120 respectively. A drain of the driving TFT 112 is coupled to the anode 118 of the light emitting element 116.
In general, an active layer of a thin film transistor of an AMOLED display is formed by a low temperature polysilicon process to satisfy with a heat-resistant temperature of a glass substrate of the AMOLED display. The active layer formed by the low temperature polysilicon process has several advantages such as high carrier mobility, high integrated driving circuit capability and low electric charge leakage. However, in addition to the above mentioned advantages, AMOLED displays need to have high storage capacitance and high aperture ratio.
Therefore, a layout design for a capacitor of an OLED display panel that satisfies the requirements for high storage capacitance and high aperture ratio is desirable.